Wednesday, September 18, 2013

Some years ago, I started using interactive geometry software. My application of choice was Cabri, because I appreciated its mathematical depth and the elegant simplicity of its interface. I developed a number of Cabri-based activities, many of which you can find on my Web site. For example:

Later, I started working with Cabri 3D, a beautiful extension of interactive geometry to the third dimension. You can see some of the resulting work on the site (3D geometry of the parabola and ellipse.)

At this point, Cabri 3D faces no competition. Yes, CAS software can graph in three dimensions, but that is not geometry in the same sense. Google's SketchUp is great at what it does, and probably can find some great uses in the classroom, but again, it is not geared to geometry. For example, try to create a regular dodecahedron with that software. It's possible, but there is just no comparison with Cabri 3D where the dodecahedron is provided as one of the tools, and where building one from more basic tools makes for a challenging and accessible lesson. I enthusiastically recommend this application.

On the other hand, there are many alternatives to Cabri in two dimensions. Geometer's Sketchpad was the main option for a long time, and there are many others. A more recent entrant in this field is GeoGebra, which is open source and free. Its design is largely inspired by Cabri, but it goes further, offering CAS, an elementary spreadsheet, graphs as first class objects, an input line, and more. Because it is available for free, it has dealt a near-fatal blow to both Cabri and Sketchpad. Both of these programs have aspects that are superior to GeoGebra, and have made gigantic contributions to the intelligent use of computers in the math classroom, but I'm afraid they are not able to compete with free.

Because of all this, I have decided to learn GeoGebra, and to post my creations on this site. This will include some activities that use the graphing calculator and some that use interactive geometry. To get this started, I have updated some pages and edited or added some worksheets:

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Henri Picciotto

I have retired from the classroom after 42 years as a math teacher in K-12 — from counting to calculus. I now work with teachers and schools, and I continue to develop curriculum.

I share instructional materials on my Math Education Page, and my views on math education on this blog. Also on this blog, announcements about: new pages, updates, etc. on the site; my publications; my appearances at conferences; and my other activities in math education.

--Henri

Note: All material on this blog is copyrighted. You may reproduce it for any non-commercial purpose, as long as you credit me and link to the blog. More info.

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Apologies

All the comments between August 2013 and June 2016 got deleted at once by Google when I disconnected the comments from Google+. I had to disconnect because otherwise it was impossible to remove spam. Apologies to all the commenters.